Vice Secretary-General Yukio Ubukata was on Thursday stripped of his role in the party for making similar comments against Ozawa.

Speaking of Ozawa and his role in a funds scandal, that has led to the arrest of his former aides and helped to send the popularity of the DPJ into decline, Ubukata said: "He should explain to the public what happened. And if the number of voters that think he should resign does not drop after that, he must step down."

If this does not happen, Ubukata said the DPJ "cannot fight the House of Councillors election this summer."

Prime Minister Yukio Hatoyama said he accepted the decision by the party to strip Ubukata of his role, arguing that if members of the DPJ are criticizing each other "we cannot maintain discipline."

Ubukata, however, said that there are many other members of the DPJ who are frustrated by not being able to let their feelings known to the public on the so-called "money and politics" scandals which have tainted many lawmakers, including Hatoyama and Ozawa.

"I wonder if the DPJ is doing OK under the leadership of Hatoyama, who can say nothing about Ozawa," Ukubata said.

On his dismissal, Ukubata said: "It is truly ridiculous. If the party tries to handle situations like this by dismissing anybody that criticizes the leadership, how can true reform take place?"

Several senior DPJ members, however, said that they believed the decision to strip Ukubata of his role was sensible, given the public nature of the criticism and the likely damage it will do to the image of the party.